This invention relates to a method and apparatus for applying waterbased paint to a vehicle such as an automobile. More particularly, this invention relates to a paint application and circulation system for applying waterbased paint to a vehicle wherein the paint supply is near or adjacent the point of application. Still more particularly, this invention relates to a low volume content paint supply system employing methods and apparatus for supplying a high volume paint application without resulting in production downtime. Still more particularly, this invention relates to a number of features in such a system for quality control purposes and operator convenience.
The paint finish on a new vehicle is often regarded as the single most noticeable visual feature of the vehicle. When the finish is smooth, even, and attractive, owners are influenced as to the quality of the vehicle, while when contamination, paint unevenness, and other defects are present, the owner is more likely to complain to the vehicle dealer, and attribute a lack of quality to the vehicle itself. Accordingly, vehicle manufacturers and paint suppliers have expended vast amounts of money, effort, and ingenuity to produce quality paints and high quality yet efficient methods of applying those paints to the surface of the vehicle.
It is well known that automotive vehicle production is automated to a significant extent. Indeed, paint is applied to the vehicle while traveling an assembly line by positioning paint booths through which the vehicles travel to receive various coatings of paint. Such techniques are highly developed and include the use of robots to apply the surface paint to the vehicle and to paint door jambs and the like. In the past, paints have used structures housing solvent-based paints which must have special explosion proof features such as grounded electrical connections and pressure releasing walls which respond to an explosion, and be located away from the factory. Such requirements of explosion proof systems for high volume storage of either waterbased or solvent-based paint are necessary for safety, but are costly when handling high volumes of either waterbased or solvent-based paints. The capital expense for such structures and long piping lines, with the accompanying pumping cost, is high. Moreover, the amount of paint in the lines which is effectively inventoried is high. For example, a line of 3000' for example, could contain more than 500 gallons of paint which is lost during color changeover, or if there is a change in the paint. In addition, prior paint circulation systems utilized large storage tanks wherein the entire content might be lost or its quality affected during changeover.
When the paint supply is located at such a distance from the point of application, significant pumping energy is required for the viscous paint. The friction generated by pumping for such long distances, and the fact that the piping may be required to pass through hotter areas of a factory, en route from the structure housing the paint to the paint booth locations in the factory, tend to increase the temperature of the paint, affecting its viscosity. Therefore, heat exchangers or other temperature control devices are usually needed to maintain the paint temperature stability in such a paint system.
Solvent-based paints have the potential for drawing environmental attention to the solvent emissions during utilization. Primer coats and clear coats have a high application efficiency when an electrical potential is used, so that solvent emissions can be reduced. However, unfortunately, color coats are adversely affected by the sole use of an electrostatic application, so that their application efficiency is low and their solvent emissions are higher.
Thus, it is desired to utilize waterbased paints to address environmental concerns resulting from the use of solvent-based paints, while maintaining the quality of the finish on the vehicle.
Moreover, it is a problem in such paint circulating systems to reduce the capital expense for preparing painting systems, and to reduce the amount of paint in the painting lines which is lost during paint changeover, or if there is a difficulty with the paint. In addition, it is a general overall aim in developing and implementing a paint recirculating system to provide for ease of maintenance and replacement. These and other objectives are met by this invention.
Thus, it is an overall general objective of this invention to provide a paint recirculating system wherein a waterbased paint source and the paint system is located adjacent to or near to the point of application in lieu of a typical paint supply source located a great distance from the application point.
It is an objective of this invention to provide a waterbased paint system which uses handling procedures and monitoring methods to reduce the paint volume contents of a local relay room for the paint system to provide a safe environment.
It is another overall objective of this invention to provide a low volume waterbased paint supply source for a high volume usage spray painting application which uses methods and apparatus for assuring that the paint supply is not interrupted.
It is another overall objective of this invention to provide a waterbased paint recirculating system which uses a single line for supply to the waterbased paint drops and return to the circulating tank.
It is another objective of this invention to shorten the piping run from the paint source and the circulating tank to the point of application for a waterbased paint, thereby reducing the amount of paint inventoried in the line and thus reducing the cost of replacement when necessary.
It is another objective of this invention to provide a local booth side system to achieve a major cost reduction of a high purity stainless steel system.
It is still another feature of this invention to provide a piping system which avoids locations which tend to induce paint buildup or sedimentation by using, for example, stainless steel piping which is orbitally welded and then passivated.
These and other objectives of this invention will become apparent from a detailed written description of the invention which follows taken in conjunction with the accompanying drawings.